Cattails: A Good Idea to Combat Global Warming and Ocean Rise

In California, where cutting-edge technologies meet practical applications, a marsh of cattails risings across the road from a field of corn offers the next best hope for rising seas attributed to global warming.

This 15-acre patch of wetlands is the U.S. Geological Survey’s (USGS) last-ditch stand against rising waters on Twitchell Island, where subsidence (sinking land) meets rising tides.

The Delta islands off the coast of California, about 30 miles south of Sacramento, are being decimated by wind, rain and farming, their fertile but friable peat soils losing the battle against time. Many are 20 feet below waterline, and only a series of levees prevents them disappearing into the surrounding sea.

Less than 6 square miles in size, they stand between the rising waters and the San Francisco bay, where an influx of sea water would damage the Delta, permanently removing the endangered smelt and making the water unusable to cities and farms to the south.

It’s hard to imagine innocuous, fluffy-headed cattails as a solution, but these marsh lovers can grow over six feet tall, and when they die (as they do every fall) they build up the soil. In fact, cattails – which tolerate almost any soil, and reproduce from both roots and seeds – are so invasive that home gardeners are warned against planting them, and wetland conservationists wage a continual war to eradicate them.

The USGS has been working with these aquatic denizens for more than 15 years. The cattails are assisted in their soil-building effort by tules (or Scirpus californicus, a native species of giant bulrush). Those who have lived in California known the tules not for their growth habit but for midwinter fogs named after them. These tule fogs blanket roads and towns so densely winter driving is almost as hazardous as in the nearby mountains, and asthma sufferers are warned to stay inside.

Is the project working? The USGS says the soil has risen one to two feet since the first plantings in 1996. As an added benefit, the cattails and tules are also removing more than their share of carbon dioxide, or CO2, the gas held mostly responsible for global warming.

With such successes under their belt, the USGS and its partners at UC Davis plan to expand the project to an additional 400 acres in 2009. Eventually, if cattails and tules prove superior in capturing CO2, Delta growers will be asked to plant these odd and largely inedible crops in a process known as carbon-capture farming. Presumably, subsidies or carbon credits will also come into play to make up for the lost income.

Three concerns stand at the forefront of this experiment. First, to what extent will flooding land to create cattail farms raise nitrous oxide (another greenhouse gas) levels, and, second, how will planting cattails instead of crops like corn exacerbate the already high cost of corn-derived foods? Lastly, carbon-capture cattail farming may release some of the mercury deposited in Delta waters as a result of extensive gold-mining operations in the Sierras more than 150 years ago, and this would be bad news for consumers eating Delta-grown corn, rice and alfalfa.

If all the obstacles – including a rising mosquito population – prove surmountable, Northern California’s Delta land may soon sport acres of fuzzy-headed cattails and sleek-stemmed bulrushes. For those concerned about rising commodity prices and their impact on world food supply, I know for a fact from my Native American grandmother that cattail roots are good eating whether boiled in soup or fried like potatoes. I don’t know if they can be dried and ground into meal for tortillas, like flour, but nothing would surprise me. Meeli, my grandmother, used to gather and grind acorns when the winter wheat crop failed.